Circle Formulas (mmm...pi!)

Round & Round

Radius, Diameter, circumference, area... they're all as easy as pi... if you understand them! Let's master these skills in order to excel on the GED.

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Your GED test will likely have a circle problem or two- and they show up in different forms. You may be asked to find the circumference or area of a circle, but could also be asked to work backwards and find the radius or diameter. How to tackle these problems?

  1. Choose the appropriate formula from the GED formula sheet

  2. Substitute in any known values. Be careful to read the problem carefully to decide whether you should use an approximation of pi (3.14) or you should keep your answer "in terms of pi" with the goal of finding an exact answer.

  3. Use your algebra skills to solve for the missing information.

Watch the Virtual GED Class video below for a complete explanation and tons of worked example problems.


Circle Formulas Beginner


Straightforward circle problems, plenty of practice of each new skill. See example videos #1-4

Circle Formulas Beginning


Mixed circle formula problems. See example videos #3-5.

Circle Formulas GED Style


Area and perimeter in terms of pi; applications of circle formulas. See the challenge and extension videos.


Example 1

Example 2

Example 3

Example 4

Example 5

Challenge 1

Challenge 2

Challenge 3

Challenge 4

Challenge 5

Extension 1

Extension 2

Extension 3

Extension 4

Extension 5

Challenge 6

Challenge 7

Extension 6